Angiogenesis - Protease production

The major factor in the initiation of new blood vessel growth (angiogenesis) is tissue ischemia (reduced blood supply), resulting in cellular hypoxia and upregulation of vascular endothelial growth factor (VEGF). VEGF induces a number of important early steps in angiogenesis, including protease production, which results in basement membrane breakdown, increased vascular permeability, and vascular sprout formation.

The angiopoietins (Ang1  and -2) play important roles in vascular maintenance and remodeling. Whereas Ang1 appears to be constitutively expressed in the stable, quiescent vasculature (blue ovals), Ang2 (yellow diamonds) is upregulated by VEGF and contributes to destabilization of the endothelium by blocking the effects of Ang1, thereby facilitating angiogenesis

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